1. Field of the Invention
The present invention relates to a communication method for data transfers between two communication devices connected over a network.
2. Description of the Background Art
Even if a network connection is established between two communication devices, data communication between the devices is not possible or the transferred data will be invalid unless two conditions are met. First, data sending and receiving between the devices needs to be enabled, second, both devices need to handle the desired data types, data formats, data size, and other parameters. Communication between devices has conventionally been handled with proprietary communication methods defined by the equipment manufacturers. Examples of these communication methods include the device on the data transmission side determining whether it can transmit data or whether it can send the requested data; comparing the types of data that can be sent by the transmission-side device and the types of data that are valid on the reception-side device to determine whether the data types are compatible between the sending and receiving sides; and acquiring the type and size of data that can be transmitted by the transmission-side device and data identification information for communication. Parts of these different methods can be omitted or combined together to build a desirable communication system and method for executing a specific communication sequence. This is described, for example, in Japanese Patent Laid-Open Publication (kokai) H9-244942.
When data communication is attempted using various combinations of data types, formats, and size, communication traffic increases and the data transmission rate decreases due to the increased traffic resulting from sending and receiving invalid data and the communication devices sending data back and forth to report and confirm the communication format.
Furthermore, when data is communicated according to a defined communication sequence between the same communication devices over plural occasions, previously communicated information must be exchanged again, thus increasing the transmitted data (traffic) and lowering the data transmission rate.
In a communication environment in which a large file, for example, must be divided for sending and receiving, how files are divided, the size of each divided data, and other parameters are individually defined by application vendor with the above-described communication techniques, and devices running different applications cannot communicate with each other.